Ahh... I was coming on here to ask a similar question. Reading all the responses carefully.

Same with us! New piece of furniture we need to place? PIVOT!!!! Moving DD into her college dorm room? PIVOT!!! It's a running joke in our house. So is "Unagi."
Right there with you with the FOMO. Every time I read about those categories...
Those are ALL favorites in my house. Love doing an EPCOT/MK split, too. YC was a fave, but now dogs (and serious allergies and asthma here), so BC is where we've started our last 2 trips. I love how it's a bit closer to EPCOT, the sunny rooms, etc. Before dogs I just picked whichever one was cheaper since they are basically the same hotel.
GF and Poly is harder for me. I love the Poly for that relaxing island feel, but I love how quiet the GF is and how pretty it is. The pools are usually less crowded there, too. The Poly rooms feel larger to me, and I like that it's easier to get to Epcot from there, but since we tend to stay at YC/BC part of the trip it's not really an issue. Ack! So hard. I'd say go with your gut instinct on this one - sometimes the palm trees of the Poly call to me, and sometimes the GF's band, restaurants, and quieter atmosphere draw us in. You know you can't go wrong here, so that's something. Happy planning!